Telephone-exchange system



S. B. WILLIAMS, In. TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED APR. II, 1.9[8-

Patented De0.-13, 1921.

S. B. WILLIAMS, n. TELEPHONE EXCHANGE SYSTEM.

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m S I m S. B. WILLIAMS, In.

TELEPHONE EXCHANGE SYSTEM. APPLICATION FILED APR- l7, I918. u 1,400,120. latented Dec. 13, 1921.

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away/gs by A/ry S. B. WHHRMS, in.

TELEPHONE EXUMNGE SYSTEM.

APPLICATION mun APR. 11. me. 3 H 1,400,120, latented Dec. 13, 1921.

S. B. WILLIAMS, In.

1ELLPHONE EXCHANGE SYSTEM.

AlilICAHDN FILED APR-17.1933.

Patented Dec. 13, 1921.

10 SHEETS-SHEET a.

lnvemar." Samuel B. Williams/1.

S. B. WILLIAMS, In. TELEPHONE EXCHANGE SYSTEM. APPUCATIDN FILED- APB. IT, IQH]. ,40 Patented Dec.13,1921.

I0 SHEETS-SHEET l3.

S. B. WILLIAMS, JR.

1ELEPHUNE EXCHANGE SYSTEM.

APPLICATION HLED APR. 17, IBIS.

1,400,120. Patented Dec. 13, 1921.

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7 van for. Samue/ 5. W/Y/MmfJK S. B WILLIAMS, JR. mwmmsz EXCHANUE SYSTEM.

1 AJPUCMHIN FILM] APR. :7, IBIS. 13,

l0 SHEETSSHEET 9- /m/en/0/ Samae/B. l V/Wfams/r S. B. WILLIAMS, JR.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION mm APR. II. I918.

1,400,120, Patented Dec. 13, 1921.

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men n .wxmims, 1a., or BROOKLYN, NEW YORK, assmuon 'ro wns'rmm ELEG- TRIO COMPANY, INCORPORATED, YORK.

on NEW You; H. Y., A coaronuzox or'miw TELEPHONE-EXCHANGE SYSTEM.

T 0 all whom it may corwe'm:

Be it known that I, SAMUEL B. WILLIAMs, Jr., a citizen of the United States, residing at Brooklyn, in the county of Kings and State of New York, have invented certain new and useful Improvements in Tele hone Exchange Systems, of which the fol owing is a full, clear, concise, and exact description.

This invention relates to telephone exchange systems, and more particularly to systems of the type employing automatic switches for distributing calls from telephone lines to the connecting circuits of opcraters positions. I

The object of this invention is to provide a system of the call distributing type in which calling subscribers lines shall be extended to operators positions with a. mini-5 mum of delay; in which each call that is originated shall be promptly and certainly seized by a single call extending circuit, and shall be extended by means oftthat circuit 'to a single available operators position, and

a single connecting cord at that position; in which, a plurality of calls simultaneously originating in the saine grou of subscribers lines shall be extended to di erent operators connecting circuits speedily and without interference ,with each other; in which the automatic switch that extends a callin line to an idle connecting circuit of an available operators position shall repeat its operation in case it fails at first to extend the call, and shall do this without losing i'tsconnection with the calling line; inwhich the calling line shall be connected with the operators telephone the instant the operators' position is selected. and in advance of the selection of the connecting cord circuit; in which the establishment of this preliminary connection or by-path to the operators telephone shall render the operators position instantly inaccessible to other calls, and shall hold the position inaccessible subject to the control of the calling subscribers switchhook; in which the continuity of this preliminary connection or by-path-shall be under the control of the listening keys associated with the connecting circuits of the corresponding opcrators position; in which each ('Zlll-(Xttlltllllg circuit shall have a bypath branch to each of the operators positions, each operator's position shall have a by-path branch to each of the call-extend- Specification of Letters Patent.

' Application filed April 17,

Patented Dec. 13, 1921.

1918. Serial No. 229,035.

ing circuits having acces to the osition,

and these branches shallbe controlle by by V path switches associated with the operators position and cord selecting switches, the operation of the by-path switches being under the control of those parts of the switch structure which also serve to control the selective operation of the switch; in which the setting of the apparatus which controls the selection of a particular available operators position by the call-extending circuit shall be maintained during the operators selectlng operation, to prevent the selecting operation from being interfered with by another position becoming available duri the selecting interval; in which the setting of the apparatus, however, shall be made periodically responsive to the availabilit of the operators positions, in case all positions were at first available, so as to afford an opportunity to change the setting in case one of the positions becomes available; in which a signal shall be displayed at each of the operators positions in case all of the positions are either busy or vacant; in which an indication shall be automatically given the operator with respect to the class of service of the calling line, and in which the operator shall also be provided with means for displaying a signal that informs her of the identity of the calling line; in which the operation of the class-of-service signal and the identifying signal shall be effected over the same conductor in such a way that the other; in which, during the resetting operation of the class-of-service device, that device 'shall b e made unresponsive and the operators position sh gggbe made unselect able; in which the operator shall be rovided with means for enabling her to old the calling line connected with the connecting circuit to which it has been extended and at the sague time permit thecalling l' e to call and be called; in which the opera r shall be able, while the calling line is thus held, to determine its busy or idle condi tion: in which the busy or idle condition of the calling line thus held automatically determines the operation of apparatus that controls the connection of various devices with the connecting circuit; in which the operator shall be provided with means for applying current to the connecting circuit for operating toll devices associated with t'wo grou the calling lines, the switch that controls the operation of the connection register being operable to apply cu'rrcnt to the connecting circuit only when the connecting circuit is connected with the calling line; in which one of the toll-device-operating keys shall be so arranged as to effect the actuation of the toll device and then cause the discon-.

and apparatus through the medium of which 'paratus w the lines control the switches; Fig. 2 shows 25 one finder circuit complete. with enough of two other finder circuits to illustrate the relationship that exists between the finder cir "cuits of a group; Fig. 3 shows two cord selector switches of a single group or frame with their associated selection-controlling ap paratus and circuits, together with similar apparatus and circuits for the cord-selector 'switches (not shown) of another group or frame; Fig. 4 shows a portion of one of the plurality of connecting circuits with which each operators position is prov ded; Fig. 5 shows a part of the position apparatus and circuits of one operators position; Fig. 6

' shows the part of the operators position ap ich controls the application of current for operating the line register and theposition register; Fig. 7 shows the extension of the-connecting circuit of Fig. 4

to the'calhng plug'and its associated appa ratus, and also indicates the switch terminal of a called line; Figs. 8 and 9 show the distributer switch mechanism by means of which the lines of the 'group 'are brought into operative relation with the linefinder starting circuit Figs. 10. 11, show difi'erent views of the class-of-service Lad,

13 and 14 switch, Fig. 10 being a bottom plan View, Fig. 12 being a top plan View. Fig. 11,:1 side elevation, Fig. '13. a detail of the armature and driving mechanism, and Fig. 14, a detail ofa portion of the contact bank with its associated wiper brushes; Fig. 15 shows a side'elevation and Fig. 16 an eud elevation 0f the interrupter for producing the classof-service, pick-up and resetting impulses: Fig; 17 shows'the switclecontrolling disks of the interrupter illustrated in Figs. 15 and 16; Fig. 15:? is a erspectirc ricw of one of thcbvpath switr tee with which the selector sw'itcr may be provided. together with the Other objects to which this associated selector-switch brushes and the operative connections with these parts; and

19 shows a detail of the operating mechanism for the by-path switch of Fig. 18.

F igs. 1 to 7, inclusive, taken tpgether, and arran ed side by side" in the manner indicated y the lines that extend to the margins of the .drawings illustrate its much of the complete organization of thesystern as is necessary to enable the construction and mode of operation to be understood Two telephone lines are indicated in each of the two groups LG and LG Show; in Fig. 1, it being understood that each group may comprise a number of such lines. The ordinary practice is to, give thefinder-swi'tchbrushes access to the terminals of fiOO-lines, these lines bein divided into ten groups. of 50 lines each. Fachof the groups of'lines has associated with it a. distributer switch: 130 to the stationary contact terminals of which the lines of that group extend, the brushes of the distributer switch being connected with group apparatus which is,actuated by the passage of the brushes over the terminals of the callin line, achof the lines has associated with it at the central ollice, a connection register 92 or a resistance coil 91. Each line is also provided withone or more spring-jacks'l by means of whichconnection may be made with the linev when it is called. The lines represented as callinglines in Fig. 1 and the line indicated as a called line. in Fig. 7, may be lines of. the same sort, similarly equipped and located. at the same exchange; or t 1e lines ma be located at diflerent oflices. Each of t e lines of the various roups is connected with a class-of-service interrupter. 179, which may be common to the' exchange; and .each of thelines also hasconnection with'and is represented by a lamp on.a commonflamp board 15.

The groups oflines have access to groups of connecting circuits through the medium.

of finder circuits F, F and F. These finder circuits terminate upon the brushes of pairs of finder and selector switches, of which two sets, LF andCS and LE and OS are shown. The startingbi the .finder switches to find the calling lines is effected by. thedi'stributer-switch .apparatus through the medium of starting apparatus, .including the relays 20, 23 and 24, which iscommpn to-all of the line groups and to all of the find'er circuits having access to they lines of these groups. Each of the groups of connecting circuits, to which the linesofi the various groups have access by way of the finder circuits F, F and F is associated with a par ticular operators position. The apparatus of only one position is shown, the others being similarly equipped. Each operators position is provided with a number of plug terminated connecting circuits extending to multipled groups of terminals upon the cord selector switches; and the brushes of each cord selector switch are given access to the terminals of a number of such groups of connecting circuits. Only one of the connecting circuits is shown complete, the other con necting circuits in the associated group and in the other groups being similarly organized and connected. The multiple connection of the connecting circuit with the terminals of the cord selector switches are shown in the case of the connecting circuit that is completely illustrated and in the case of a single connecting circuit that is indicated in another group; and in like manner the multiple connections of the telephone line with the terminals of the line-finder switches are shown in the case of the lines that extend from stations A and A. The multiple connections that exist between corresponding sets of switch terminals in the case of the other connecting circuits and telephone lines are omitted in order to simplify the drawing.

A number of groups of cord-selector switches, like the group illustrated in Fig. 3, may have access to the same groups of connecting circuits and their corresponding operators positions. This is indicated in Fig. 3. Each of the groups of cordselector switches has associated with it certain selection-controlling apparatus, that associated with the cord selectors shown in Fig. 3, appearing under the caption Frame 2, and that associated with another group of cordselector switches appearing under the caption Frame 1. The selection-controlling apparatus for each frame or group of cordselector switches comprises a pair of relays 77 and 93 for each group of connecting circuits or operators position, to which the cord selector has access, and a group of is lays 61, 63, 64,. 66 and 67 common to all of the first-mentionedgroups.

Each of the operators positions is provided with apparatus which is common to all of the connecting circuits of that position, and which any be brought into association with any of the connecting circuits either automatically in the extension of a call to one of the connecting circuits, or at the will of the operator in the course of her supervisor operations. The opera tors common or position apparatus is illustrated in Fig. 5 and Fig. 6, and each of the connecting circuits with which the operators position is equipped may have connection with the position apparatus in the same way in which the connecting circuit illustrated in Fig. 4 is shown to have connection with this ap paratus.

'I l 1 e iine finder switches LF and LF' and the cord selector switches CS and CS may be substantially like the switch illustrated and described in Patent No. 1,177,044 to James L. lVTcQuarrie, issued March 28, 1916.

The line finder and cord selector switches are alike in all substantial respects. Each comprises a longitudinally movable shaft 1, carrying as many sets of brushes 2 as there are groups of stationary terminals to be engaged. To move the shaft up, an extension at the lower end of the shaft is brought into engagement with the constantly rotatin power member 3 by means of an idler whee operated by the up-drive magnet 32; and to move the shaft down, the extension is brought into engagement with the power member 4 by means of an idler wheel operated by the down-drive magnet 62, Normally, the brushes of each of the sets 2 are held apart so as to clear the associated terminals by means of a separating cam 5 located between the innermost brushes of the set. The cam 5 is rotatably mounted, and when rotated in one direction, releases the brushes and permits them to engage the as so'ciated terminals. The tripping or releaS- ing of the brushes is controlled by a number of trip magnets, as 16 and 17. Each of these when energized, rotates an associated trip rod 6 that extends transversely to the switch shafts 1 and carries as many trip yokes 7 as there are finder switches or selector switches in the group. The trip rod in rotating brings all of its trip yokes 7 into position to operate the brush-controlling cams 5 of the corresponding sets of brushes on all of the switches, so that whichever of the finder switches is caused to move up, has that set of brushes tripped that corresponds with the particular trip magnet 16, 17, that is at the time energized. When the finder switch that has been in use is re turned to its normal position, any of the associated controlling cams 5 that has been tripped, is engaged and rotated in a reverse direction to separate its switch springs again and thus render them inactive. Each of the line finder and cord selector switches has associated with it, a commutator 8 which comprises a number of stationary commutator segments and a set of movable brushes carried at the top of the switch shaft 1' and cooperating with the stationary segments. This commutator serves tomake and break a number of the controlling circuits in the various stagesof the upward movement of the switch shaft. 1

For controlling the circuits of the organization, there are employed a number of sequence switches which are shown at different points and designated 200, 300, 400 and 500 respectively. These sequence switches may be of the type disclosed in Patent 1,127,808, issued February 9, 1915 to Reynolds and Baldwin. Each consists of an electromagnetically controlled motor or driving mechanism and a number of associated switch cams. The st'iitch cams, associated with each of the sequence switches 200 are dcsig nated 201 to 221 inclusive; those associated with each of the sequence switches 300 are designated 301 to 321 inclusive; those associated' with each of 'th e sequence switches 140C} are de'signatedjm to 421 inclusive; and those associated with.-each of the sequence switches 5(30 arefdesi ated 501 to 607 inclusive. To each of -t e contacts associated with the various .s'equence switch cams are applied certain numerals. These numerals in thecase ofthe cams 201, 301, 401 and 501 indicate the" only positions of the associated SqQBhCBfSWllIEh in whichthese particular coii itacts'are open; the numerals applied to all of the othercontacts of each sequence switch indicate the only positionswofthe particularsequence switch in which the associated contacts are closed. I

The resting positions ofthe difierentsequence switches, and the stages of operation with which these positions are associated,

are as'fol lows:

Finder sequence switch 200.

.1.-Normal. I

2. Awaiting starting circuit;

3. Hunting.

4. Awaiting selector sequence switch. 5. Talking. t

18. Finder switch return.

Selector sequence switch 500.

1. Normal. 2. Awaiting preeedingcircuit. 3. Awaiting setting of operators select in'g circuit/ a. Pass by.

15. Awaiting release of operators selecting circuit.v

6. Hunting connecting circuit. 1 y

7. Awaiting listening key. sequence switch. I

8. Awaiting finder sequence switch.

9. Talking.

18. Selector switch return.

Listening key sequence switch 400.

1. Normal.

2. Awaiting finder circuit. 6. Listening in.

8. Listening out.

Calling 00rd sequence switch 500.

1. Normal. 2. Awaiting connection. 16. Talking.

The distributer mechanism 130 shown in Figs. 8 and 9 consists of a stationary drum 120 and a movable sleeve 121 mounted on a shaft 123. The shaft 123 is rigidly sup ported in the brackets 224 and 225. The stationary drum 120 is in efl'ect an armature consisting of an insulated portion 226, in which are mounted wntact segments such other arm being carried to the side of the stationary drum where it forms a terminal to which the corresponding line wire may be attached. Bigidly attached to the movable sleeve 121 'is'the gear wheel 122, the slip. rings 135, 136. and 137, and the arm 134 to which are attached the brushes 1'31;

132 and 133, the brushes being insulated from each other and from .thearm upon which they are mounted. The slip rings are also insulated from the sleeve 12l and from each other. By driving the gear wheel by any suitable means, the movable sleeve 121 will rotate about the shaft '123and thus carry the brushes-131, 132 and 133 around the periphery of the armature. The brushes, when rotating in this manner, make successive contact with the conducting segments which constitute the tip, ring and sleeve terminals of the lines assigned to this particular distributer. The brushes 13 1, 132 and 133 are electrically connected to the slip rings 135, 136 and 137. and. the brushes 440, 441 and 442 respectively cooperate with these slip rings. The terminal ends of the brushes 440, 441 and 442 are connected directly to the distributor circuit. It consequently follows that as the brushes 131. 132 and 133 rotate about the drurn'120, the lines terminating upon the distrib'uter will be consecutively connected to these brushes, and thence, by means of the slip rings 135, 136 and 137 and the brushes 440, 441 aiid 442, to the distributer circuit.

The classof-service interrupter shown in Figs. 15, 16 and 17, coinpi-isesa number of sets of switch springs operated by the cams 171 to 17.7,,inclusive, carried upon the shaft 178. The shaft 178 has its hearings in the s'tandards'l'l and 71', and rotates continuously, being driven in any suitable manner through the medium of the gear wheel 179. Each of the sets of switch springs associated with cams 172 to 176, inclusive, consists of two springs the contacts of which are normally in engagement. Each of the two sets associated with the cams 171 and 177 consists of two springs the contacts of which are normally open. The cams 172 to 17,6. inclusive, are so formed as to cause. one, two, three, four and five breaks per revolution respectively in the normally closed circuits controlled b the associated sets of switch springs. The cams 171 and 177 are so formed as to cause one closure-per revolutively, in the circuits controlled by the 21SSO- ciated switch springs. The cam 171 and its associated switch s rings control the production of the pic -up impulses, the cam class-of-servlce impulses, as will be described hereinafter.

The class-of-service switch, shown 111 1 Figs. 10 to 14 inclusive, is of the so-called :Dietl type. It includes three sets of brushes or-wipers, 272, 272' and 272, carried on a common insulating hub mounted. on the contact terminals opposite the space which brushes that are electrically connected so,

spindle 269 and radiating; at an angle of one hundred and twenty egrees from each other.- These brushes or wipers engage a circular row of, contacts 274 and insulated segments 273, 273' and 273. Each of the segments 273 extends over a little less than one-third of the circle, there being in the specific switch illustrated siirteen contact terminals opposite each segment and two lies between each segment and its adjoining segment. The wipers 272, 272' and 272 are insulated from each other, and each wiper consists of two switch springs or that each wiper serves to connect the particular contact terminal which it engages tact terminals.

with the contact segment which lies opposite that terminal. The radiating wipers are unidirectional in their movement, so that each wiper coiiperates successively with the three segments and their associated con- The rotation of the spindle to cause the movement of the wipers is effected by means of the electromagnet 271 acting through the edium of theratchet wheel 279 and pawl 2 5. The'pawl 275 is carried upon an arm secured to the armature 278 of the electromagnet' 271. The armature 27 8 is centrally pivoted so as to be oscillated when the electromagnet is energized, and is returned to its norma position upon the d'energization of the magnet by the helical spring 276, the

tension of which ,may be adgusted by the wing 268. The contact terminals with their associated-contact segments and brushes or wipers are mounted upon a plate270, carried upon the supporting frame 270'. The electroma st 271 with its associated armature, rat et wheel and spindle are mounted n a plate 270', which plate is secured to he plate 270 by a screw ahTslot connection. The driving or operating parts of the switch and the circuit-controlling parts of the are thereforeflreadily separable from each other and from the supporting frame, The operating circuit of the electro magnet'271 is carried to the electromagnet through the knife switch 271, so that the circuit isautomatically broken and made as the plate-carrying magnet is removed from and replaced upon the plate 270.

In outline, the operatlon of the system in the embodiment disclosed is as follows: When a subscriber calls, the passage of the brushes of the distributer switch 130 over the terminals of the calling line records the call in the distributor apparatus of the associated group, and this recorded call causes the closing of the starting circuit common to all of the distributor groups and to all of the line-finder switches that serve these groups, and also causes the cnergization of the finder switch trip magnet corresponding to the group of lines in which the calling line is located. If the startin circuit is at the time being used by some ot er calling line, the recorded call is held until the starting circuit is freed. As soon as the call is discharged into the starting circuit, the distrihuter apparatus is released and made available for recording-another call in the same group.

The finder switches each have as many sets of brushes as there are groups of lines. The closing of the starting circuit causes a preselected one of the finder switches to move its brushes, and the energization of the trip magnet makes active the set of brushes corresponding with the group in which the calling line is located. The ap paratus which brings about the energize.- tion of the trip magnet operates toprevent temporarily the trip magnets| of other groups of lines from being energized by calls that may at thetime be initiated in the other groups.

As soon as the; brushes of the finder switch are tripped another finder switch is brought into operative relation with the starting circuit, and the starting circuit is released and made available for the use of calling lines in groups other than the grou in which the first-mentioned calling line is located. \Vher'; the new finder switch is connected with the starting circuit, any other finder switch is prevented from being brought into operative relation with the starting circuit, so that the starting circuit has control over only one finder switch at a time.

When the brushes of the started finder switch compllete connection with the the teris continuously under the control of the op erators positions, and keeps a path prepared for energizing the trip magnet representing the fi-rstavailable position in the series. The finder circuit that is extending the call sends a tripping impulse over the path thus prepared, and when the tripping magnet operates, the upward movement of the cord selector switch is started. At the outset of this movement the set of brushes is tripped that corresponds with the reselected operatorsposition, and immediately thereafter the common selection-controllin apparatus is released and made available or controlling the selection of other operrfiors positions by other cord selector switches and finder circuits. During this selecting operation, the setting of the selection contro ling apparatus is maintained, so that the tripping impulse is prevented from passing to the trip magnet of some other position which in the interval may have become available. If all of the operators positions should be unavailable at the moment the finder circuit is ready to extend the connection, the finder circuit is held and the availability of the operators positions is periodically tested by the selection-controlling apparatus until one of the piisitions becomes accessible, whenithe operation is proceeded with.

After the set of cord selector brushes has been tripped, it continues its upward move ment, successively engaging the terminals of the connecting circuits located at the open ators position that has been selected, and stops upon the terminals of the first connecting circuit encountered that is idle and avaib able for hse. If ,for any reason, the brushes should fail to be stopped upon the terminals of a connecting circuit, the cord sclcctor switch isrcturncd to its normal position, and the selecting operation is then repented.

Prior to the extension of the connection to the connecting circuit, and at the instant that the operators position is selected and the corresponding: trip magnet energized, a signo] is displayed at the o erator's position which notifies the operator that her position has been selected and that a call is coming. At the same instant, a byputh is closed that puts the operator immediately into telephonic communication with the calling subscriber. and the listening-in keys associated with all of the connecting cords of the position are rendered inoperative so that the operator cannot interfere with the coming call by listoning in on a cord circuit after the position has been selected and before the call arrives. e operators position at the same time is made lnaccessible to other incoming calls.

hen the cord selector switch stops on the terminals of the selected connecting circuit, it li' hts a lamp associated with that circuit at t operators position, and substitutes a ator to inform herself of the identity of the calling line is made operative. The operators control over the listening keys has in the meanwhile been restored so that she may, if she desires, listen .il: on any other connection.

When the operator has rcccii ed the calling subscribers instructions she tests the line that is called for and, if it free. inserts the calling plug into the called line sprininjnch.

is act automatically brings about the dis connection of the operators telephone apple rutus from the circuit and the restoration of the rl:iss-of-service signal mechanism, the

operators position being rendered unselcct able and the lussof-service mechuuisrn boiug prevented from being brought into operative l'tlilllflllritltll no connecting circuit While the restoration is being effected llhcn the subscribers l; c finished their conversation. the operator elicits tllh\"i3fint ltion by pressing the discounc-t he) and withdrawing the calling plug. if the calling line is a measured service line, the operator presses a key which registers thicsil on lilo line register and the position register upon the dcpression of the he and ii' ee the connection upon the role of tin.- This key is cl'lcctivc to apply register operating current to the connecting: cirimit only when the (Ulllltllllllg circuit is crtcndcd to u culling line. If the culling: subscriber wishes a secondconnection. ihc oicrutoi presses another key which registers tic cuil on the line and position rc gistcrs, but does not disconne t the cuilhu, linc from the ciumccliiigf circuit liet'oi'c performing thc disro wing; or riggis torinp' operations i'lflll'lb dmrc, the ope-h :itor supervises by pressing hr listening-in her, which nct contact-ts b r ..,ii'jlllfiil( with some time again actuthc ircuit and at the ates the clussof-scrvirc mechani m to guide hcr in making the charge or registration.

i' the operator is unable for any reason to give the culling subscriber connection with the called line, she presses a hohiling hey which maintains the connecting circuit in connection with the calling line. but with draws the busy test from the line that it may call and be called. By listening in on 21 called line thus held, the operator is given a busy test if the line is'in use, the class-ofservice signal mechanism under these circumstances not being ope rated. If the line is free when the operator listens in on the held connection, she may restore the holding key and proceed with the establishment of the connection in the usual way.

The features of the operation that have been set forth in outline in the foregoing, together with other features present in the system, will be fully explained in the detailed description that follows.

It will be assumed that the subscriber at station A takes his receiver from its switchhook. The brushes 131, 132 and 133 of the distributer switch 130 are constantly rotating, and thus are successively bringing the cut in relay 11 and the test relay 12 into tem orary association with the various lines of t e line group LG which the distributer switch 130 serves. It a line is in use; either as a calling line or as a called line, its sleeve conductor 53 is connected through relatively low resistance with battery of the same potential as that to which the winding of the cut-in relay 11 is connected, as will hereinafter be explained. Consequently, when the distributor brush 133 engages the sleeve terminal of such line, the cut-in relay 11 remains inert. But when the distributer brush 133 engages the sleeve terminal of a line that is not in use,-an energizing path is closed for the cut-in relay 11 by way of the brush 133 and the sleeve resistance 91, or the gizing and looking message register 92 associated with that line. The test relay 12, therefore, is connected with the two line conductors 38 and 39 of each line that is not inuse, and when it is thus connected with the conductors of the line extending to station A, at which the telephone receiver has been removed from its switchhook, the test relay 12 attracts its armature and closes a circuit that extends from battery through the winding of relay 9 to ground by way of the front contact and armatureof relay 12. Relay 9, in' operating, closes a locking circuit for itself by way of its left-hand tront contact and armature and the' left-hand back contact and armature of relay 10. The distributer brushes do not stop upon the terminals of the calling line, but continue their rotation, the effect of their engagement with the calling line terminals being in effect to record the call by ener- V up the relay9.

The effect of recording the call upon the relay 9 is to cause the starting of one of the finder switches LF, LF, etc., which serve the lines of this and the associated line groups. This is accomplished through the medium of a starting circuit, two of the conductors 57 and 58 of which are extended to the relays 19 of the various line groups LG. LG, etc. Assuming that the starting circuit is not in use at the time the call is recorded on the relay 9 of the line group LG, the operation of this relay closes a circuit that extends from battery through the lefthand armature and back contact of relay 23, ri ht-hand armature and back contact of re ay 24, conductor 57, right-hand resting contact and switch spring of relay 19 of group LG, the windings of relay 19 and the associated trip magnet 17 in parallel. lefthand switch spring and resting contact of relay 19, right-hand winding of relay 18, and right-hand front contact and armature of relay 9 to ground. The closure of this circuit causes relay 18 to operate; and in operating relay 18 closes at its left-hand front contact and armature a shunt path by way of its left-hand low resistance winding to ground that sufficiently increases the current flow in the circuit to bring about. the operation of the relay 19 and its associated trip magnet. 17, the relatively high resistance of the right-hand winding of the relay 18 preventing the relay 19 and its associated trip magnet from bein operated at the initial closure of the circuit. Relay 19, in oper ating closes a circuit that extends from battery by way of the left-hand armature and back contact of relay 23, windin of the starting relay 24, conductor 58, the righthand armatures and resting contacts of other relays 19 in the series, right-hand armature and switch spring of 'the relay 19 of group LG, the windings of rela 19 and associated trip magnet 17 in paralle and the left-hand switch spring and armature of relay 19 to ground. The closure of this circuit operates relay 24 and the trip magnet of line group LG tostart a line-finder switch and trip the brushes of that switch, which correspond with the line group in which the calling line is located, as will hereinafter be described. This circuit is maintained and the trip mag net 17, starting relay 24., and group relay 19 held energized until the relay 23 is actuated at a later stage of the operation, as willbe described. I v

When the recorded call has thus brought about the energizatio of the starting and brush-tripping circuit, the call recording apparatus including the relays 18, 9 and 10 is disconnected from the starting circuit and the record obliterated by the releasing and return of these relays to their normal condition. When the recording apparatus obtains access to the starting circuit, the operation of the relay 18 not only brings about the energization of the starting and tripping circuit by closing at its left-hand front contact and armature the low resistance ath to ground; but it also closes a circuit that extends frombattery through the winding of relay 10, and the right-hand front contact and armature of relay 18 to ground. The closure of the circuit causes relay 19 to open, at its left-hand back contact and armature, the locking circuit of the relay 9. Relay 9 in releasing opens at its right-hand front c rtuct an! or! way of u iznliiig atinu. has spring .mll

giicing lu' lll th 01 3 in re its, rightthe curry the with to ground by Land s. high resistance r Belay 19, in operei its lcft-hand switch *oiulact the main ener- Jeluy 1H. Relay 18 in doingso, opens at ontact and armature, of the relay 10, which 19 relay 5 Thus the relays l8, l3 crawling apparatus are rerun in readiness to Milling l ne.

ii that when the relay inciting circuit for itself right-hand front ight-hand winding of respond ll! ,1 i

ii? 1 ill lit! operates it c that ostenri" couizn relay 3 r and front contact and uilliu 'h oi" i-i v if to ground. This is for the pi 'pose all inst: if a continued interhilly: path for relay 9 at contact and armature of relay 5) is released. Otherpm that if the momentary operation 01' the relay it}. which operates relay it. had ocwirrcd before the distributer brushes had passed beyond the calling line ruption ol' the i the left haml h: relay ilk urti' l wise it in terminal and "ms opened the initial energizing C uil if the recording relay 9, the

recordi A and again circuit as soon he available is ill relay would remain locked up and mercies e rting and tripping circuit again became witch brushes leave the line. the test relay *1 meanwhile the i to the starting cirdescribed, the locking 1;: relay 9 has been s of the relay 10, and nitial energizing path (is of the test relay 12 s The recordcuit in the Infill"! circuit of El the brcalins i. of the re immediately in soother calling line 1 that line be the :liatcly adjoin the which the apparatus i. in this case the recording relay i ain locked up by the response of the i e relay 12 as soon as the terminals of the second calling line are engaged. and remains locked up to bring about the cncrgizz-alieu ol' the starting circuit and the starting of another finder switch just as soon as t starting circuit is released and again urn-ole available by theoperation of the relay as will hereinafter be described.

lug condition in r of the ,1: mm Wlius terminals As long as the starting circuit in use, the

"Ii-"ll in the recording relay Nirctv'e to start a finder the: availabililty of the tored.

ml, the appropriation an incoming call is call in all 9, and is switch a starting ir As l of the star accompanied bv the operation of the relay 24, and the relay 24, in operating, disconnects the conductor 57 from ground. As it is over this path to ground that the initial energization of any of the relays 19 is effected, the calling lines of the other groups are deprived of control over their associated relays l9 and trip magnets until the starting relay 24 is returned to normal. If a line in another group, say group LG, calls while the starting relay 24 is serving the calling line of group LG, the recording relay 9 of that other group is locked up and holds closed a pati to ground from conductor 57 that includes the windings of the associated relay 19 and trip magnet 16 in parallel and the righthand winding of the associated relay 18. When the starting relay 24 has performed its function in connection with the calling line of group LG and releases its armatures, the path by way of conductor 57 is 7 completed for the energization of the relays 18, 19 and 10 and the tri; magnet 16 of group LG in the manner that has been described in connection with the operation of these parts in group LG.

If calling lines in several groups are awaiting the starting relay 24, the recording relays 9 of thesegroups being locked up asa result of the momentary operation of the associated relays 12 as the distributer switch brushes pass over the terminals of the calling lines, the group, which is closest electrically to the starting rcla 2a, will have its trip magnet operated an will takepossession of the starting circuit, The reason for this is that the conductor 58 that includes the winding of th'e starting relay 24, and over which the continued energization of the relay 19' and associated trip magnet is effected, passes serially through the righthand armature and resting contact of each of the relays 19. so that the relay 19 that is closest electrically to the relay 24 interrupts the path of the conductor58 to the more re mote relays of the series.

\Vhen the relay 19 of a group is energized by its seizure of the starting relay 24, it releases the associated relay 9, as has been described. and thus again renders the relay 9 subject to the momentary operation of'the test relay 12 as the brushes of the distributor switch 130 pass over the terminals of the lines of that group. In order to prevent-the calling line from starting more than one line finder switch, the time required for the dist!" uter brushes to complate a cycle of their rotation is so regulated that the calling line will have been seized by a finderswitch, and thus deprived of its power to control the test relay 12, before the distributor brushes have again moved into position to engage the terminals of that line. i

The starting of a line finder switch when 180 he common starting relay 24 is energized s clicclcd by the closure of a circuit that extends from battery by way of the updrive magnet oi whichever of the line finder sniivhes Ll LF. etc. is next in order to he started. conductor 59, line finder sequence switch. contact Qlil (2 to 2 3 line finder sequence switch contact 217 (2). conductor and leit-hand armature and front contact of the starting relay 24 to ground. At the same time another circuit is completed from battery by way of the cord selector sequence switch contact 320 (1 to 4), windingof rela o0, selector sequence switch contact 309 Tl to 8), finder sequence switch contact 2L7 (2), and thence to ground by way of conductor 29 and the lefthand armature and front contact of starting relay 24.

Relay 3U, in operating, closes a circuit that extends from battery through the motor magnet and contact 203 (2) of the finder sequenceswitch, and right-hand. front contact and armature of relay 30 to ground. The closure of this circuit moves the finder sequence switch 200 out of position 2. Relay ll, in operating, also closes a locking circuit for itself that extends from battery by way of selector sequence switch contact 320 (1 to 4), winding of relay 30, selector sequence switch contact 309 (1 to 8), lefthand front contact and armature of relay Ill! selector switch contact 317 (1), finder SPl'illQIICe switch contact 216 (2 to 3), condoctor 25 and the right-hand back contact and armature of relay 23 to ground.

When the finder sequence switch moves from position 2 to position 3, it closes a cir uit from battery through the winding cl' npdlive magnet 32, conductor 59, finder sequence switch contact 213 (2% to 3) and the left-hand back contact and armature of test relay 5? to ground, that places the continued encrgiaa-tion of the updrive magnet under the control of the test relay 37. The test relay 37 is energized to open the circuit of the updrive magnet 32 and stop the upward movement of the finder switch brushes when the terminals of the telling line are engaged, as will hereinafter be described.

At the outset of the upward movement of the elevator rod 1 ofthe line-finder switch as a result of the energization of the updrive magnet 32, all of the brush trip levers are moved past the corresponding trip yokos 7. The only trip magnet that is energizcd in this case is the magnet 17 which corresponds with the group LG in which the walling, line is located; and consequently the only trip yoke in position to engage a trip lever on the elevator rod is the one which controls the brushes 40, 41 42 and 43 that are adapted to engage the terminals of that particular group of lines. This set of brushes; therefore, is released and made operative. and the other sets are held clear of their associated liiie tern'iinals.

As soon as the set of brushes correspond ing with the group in which the callinpij line lo ated is tripped. the group up pamtus. by means of which the lines control the brush tripping and lnnfinder starting operations may he returned to its normal position. This is eifected by the closure of a circuit which extends fron battery by way of the winding of relay all conductor 26, finder sequence switch cone-m 5212 (2% to 3) conductor 68, and segment of the line-finder commutator and its (O11'G- sponding brush to ground the closure of this circuit which tinned to occur an instant after the brushes axe tripped, and before they engage the line terminals in the upward movement of the elevator rod, relay Q3 isenergized to open, at its left-hand armature and back contact, the circuit by way of conductor 58 that up to this time has been holding the starting relay 2a and the trip magnet 17 and ciated relay .19 energized. )Vhen, an instant later, the relay 23 is dciinei'gizcd by the ground brush disengaging the coin niutator segment (i, the group or starting: circuits are again rendered responsive to a calling line.

W'hen relay 23 operates it also interrupt. at its right-hand armature and burl; con tact the previouslytraccd circuit that has maintained relay 30 of the finder circuit energized. That relay, in releasing its armatures, closes a circuit for moviup the finder Sequence switch 201) of some other finder circuit from its normal or first Inn-1ition to position "i where it is in readiness lo respond to the next operation of the starting relay 24. Assuming that the hinder circuit 1*", which may be assumed to be similar to the finder circuit F in its equipment has its parts in their normal condition, this circuit may be traced from battery through the motor magnet 200 and contact 204: (1) of the finder circuit F, finder sequence switch contacts 204 (4 to 18) of other finder circuits similar to the circuits F and F in their equipment, which may be assumed to he busy, and therefore to have their se quence switches in some positiondwtween position 4 and position 18 inclusive"tinder sequence switch contact 221 (3) or' finder circuit F, left-hand hack contact and arma ture of relay 30, selector sequence switch contact 317 (1), finder sequence switch contact 2'16 (2 to 3), conductor 25, and righthand back contact and armature of relay to ground. Thus the passing of the G segment in the upward movement of sh started finder switch restores the group and starting circuits. releases relay 30 of the associated finder circuit, and moves quence SWlLCll 200 of another finder circuit AS a result 0'? ill into position 2 in readiness to respond to the next actuation of thestarting relay 24. Provision is made for moving the finder sequence switch of one of the finder circuits into position 2. and thus rendering the associated circuit responsive to the starting relay, when all of the finder circuits are idle and have their finder se uence switches standing in position 1, or w en all of them are busy and one is released to permit its finder sequence switch to return to position 1 while the sequence switches of all of the others are in some position between 4 and 18 inclusive. This is accomplished through the medium of the relay 20, which has its energizing circuit completed by way of conductor 28 and the series of finder sequence switch contacts 214 (4 to 1) to ground at the end of the series. When this condition of the series of finder sequence switches exists, relay 20 is energized and closes a circuit that extends from the 204 cam series of all of the finder sequence switches to ground by way of conductor 27 and the front contact and armature of relay 20. The closure of this path to ground energies the motor magnet of one of the finder se uence Switches 200 by way of the cam 204 1) of the associated sequence switch to move that switch to position 2.

The condition that is now assumed to exist is one in which the line finder switch LF is moving up with its set of brushes correspending with line group LG tripped, in which the trip magnet 1 and relay 19 of that line group and the common starting relay 24 have been returned to their normal con ition, and in which the finder sequence switch of another finder circuit F 'has been moved to position 2 in readiness to respond to the next operation of the starting relay. As the tripped brushes rise they come into engagement consecutively with the sets of terminals corresponding with the difierent,

lines of the grou At the instant of engagement of the brush 42 with the cone spending line terminal 46 of each line, a circuit is closed that extends from low potential battery by way of the relay 52, sequence switch contact 209 (2 to 3), conductor 50, brush 42, line terminal 46, conductor 53, and windings of message register 92 or resistance 91 to ground in the case of certain of the lines or by way of windings of message register 92' or resistance 91' to high potential battery in the case of other of the lines.

In case a line is busy either as a calling line or it called line, a path to low potential battery exists from conductor 53, as will hereinafter appear. that serves to shunt the relatively high resistance relay 52 and prevent its operation. it a line over the terminals of which the brushes are passing is not busy, the relay :32 is operated and in attracting its armatures closes a circuit that extends from battery through the left-hand winding of the relay 37, inner armature and front contact of relay 52, sequence switch contact 208 (2 to 3), conductor 49, brush 41, line terminal 45, conductor 39 to one limb of the tele hone line, thence by way of the path control ed in contacts of the substation switchhook to the other limb of the line conductor 38, terminal 44, brush 40, con uctor 48, sequence switch contact 207 (2 to 3), outer front contact and armature of the relay 52, and rigrht-hand winding of the relay 37 to ground. he circuit traced above is not completed until the finder switch brushes engage the terminals of the calling line, as the calling line is the only line .that has its telephone-receiver off the hook, and at the same-time is not connected with either by some other line finder or by a connecting circuit calling phi The completion of this circuit energizes t e rela '37 and causes that relay to interrupt at its right-hand back contact, the circuit by way of the finder se quence switch contact 213 (2 to 3) and conuctor 59 which up to this time has been kee ing the updrive magnet 32 energized an cousin the u ward movement of the switch brus es. T erefore the operation of the relay 37 u on the finding of the calling line acts to e ect the instant 'deenergization of the ufidrive magnet 32 and thus to stop :ahe brus es on the terminals of the calling Relay 37 in operating also closes a locking circuit for itself by way of its left-hand front contact and armature and finder sequence switch contact 219 (3) to ground. It also completes a circuit that extends from battery through the motor magnet and contact 206 (3) of the finder sequence switch, and left-hand front contact and armature of relay 37 to ground. The closure of this circuit moves the finder sequence switch out of position 3.

Provision is made for preventing the movement of the sequence switches 200 of more than one finder circuit into the 2 or waiting position in case an intermediate finder circuit returns to its normal position before the started finder circuit has found the calling line and moved its sequence switch 200 out of position 3. As has been described, the passing of the G segment, by energizing and then releasing relay 23, applies ground by way of conductor 25, finder sequence switch contact 216 (2 to 3), selector sequence switch contact 317 (1), left-hand armature and back contact of relay 30, and finder sequence switch contact 221 (3), for moving out of its normal or 1 position the finder sequence switch of the next finder circuit in the series which is standing in that osition. Let it be assumed that the finder sequence switch, which is thus moved 

